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WO2018181243A1 - Accumulateur au lithium-ion - Google Patents

Accumulateur au lithium-ion Download PDF

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Publication number
WO2018181243A1
WO2018181243A1 PCT/JP2018/012290 JP2018012290W WO2018181243A1 WO 2018181243 A1 WO2018181243 A1 WO 2018181243A1 JP 2018012290 W JP2018012290 W JP 2018012290W WO 2018181243 A1 WO2018181243 A1 WO 2018181243A1
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WIPO (PCT)
Prior art keywords
secondary battery
lithium ion
melting point
ion secondary
positive electrode
Prior art date
Application number
PCT/JP2018/012290
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English (en)
Japanese (ja)
Inventor
山本　伸司
悠 水野
裕理 遠藤
Original Assignee
三井化学株式会社
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Filing date
Publication date
Application filed by 三井化学株式会社 filed Critical 三井化学株式会社
Priority to JP2019509848A priority Critical patent/JP6989095B2/ja
Priority to CN201880021244.4A priority patent/CN110495044A/zh
Priority to EP18778257.8A priority patent/EP3605713B1/fr
Publication of WO2018181243A1 publication Critical patent/WO2018181243A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/426—Fluorocarbon polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/574—Devices or arrangements for the interruption of current
    • H01M50/581—Devices or arrangements for the interruption of current in response to temperature
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/574—Devices or arrangements for the interruption of current
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a lithium ion secondary battery having a porous insulating layer between an electrode and a separator.
  • lithium ion secondary batteries have been widely used as electronic devices such as mobile phones and notebook computers, electric vehicles, and power sources for power storage.
  • This lithium ion secondary battery has the advantage of high energy density, but uses lithium metal and a non-aqueous electrolyte, so a sufficient countermeasure for safety is required.
  • the non-aqueous electrolyte secondary battery disclosed in Patent Document 1 includes a negative electrode in which a negative electrode active material layer is formed on a current collector, and a positive electrode in which a positive electrode active material layer is formed on a current collector.
  • a porous protective film having a thickness of 0.1 to 200 ⁇ m is formed on the surface of either the negative electrode active material layer or the positive electrode active material layer.
  • the protective film formed on the surface of the active material layer prevents the active material from dropping and reattaching after the active material layer is formed and before the electrode is housed in the battery can. Thereby, the internal short circuit of the battery induced by the active material reattached to the electrode surface can be prevented, and a non-aqueous electrolyte secondary battery having high reliability and safety can be obtained.
  • Patent Document 2 includes a step of applying a positive electrode paste containing a positive electrode active material and water to the surface of a positive electrode current collector to form a positive electrode mixture layer, and an insulating paste containing an inorganic oxide filler and an organic solvent. Forming a porous insulating film by applying to the surface of the positive electrode mixture layer, wherein the positive electrode active material contains a composite oxide containing lithium and nickel, and the molar ratio of Ni in the composite oxide to Li Discloses a method for producing a lithium ion secondary battery in which is 60 mol% or less.
  • the porous protective film described in Patent Document 1 can prevent the active material from falling off the electrode during production and prevent the occurrence of an internal short circuit, it can be used for nail penetration test, crush test, and overcharge test. There is no description of the effect of suppressing heat generation when an internal short circuit occurs.
  • the production method described in Patent Document 2 also provides a high-output and high-capacity lithium ion secondary battery that suppresses problems in the case of forming a porous insulating film on the surface of the positive electrode mixture layer. It is not clear about the heat suppression effect at the time of internal short circuit of the battery.
  • the subject of this invention is suppressing the heat_generation
  • a lithium ion secondary battery includes a current collector, an electrode including a positive electrode or a negative electrode on at least one surface of the current collector, a separator separating the positive electrode and the negative electrode, and between the electrode and the separator. And a non-aqueous electrolyte.
  • the porous insulating layer is made of a binder containing a mixture of polyvinylidene fluoride (PVDF) and a melting point depressant, and this melting point depressant is measured by differential scanning calorimetry in the presence of a nonaqueous electrolyte. The melting start temperature and / or melting peak temperature of the binder is reduced as compared with the case of only polyvinylidene fluoride.
  • the binder may be a copolymer of a vinylidene fluoride monomer and another fluorine-containing monomer or an oxygen-containing monomer, instead of a mixture of PVDF and a melting point depressant.
  • the lithium ion secondary battery of the present invention can suppress heat generation during an internal short circuit of the battery by forming a porous insulating layer between the electrode and the separator.
  • the lithium ion secondary battery of the present invention will be described.
  • the structure of the electrode layer composed of the positive electrode, the negative electrode, and the separator constituting the electrode element will be described based on the drawings, and then each component of the battery will be described in detail.
  • FIG. 1 is a schematic cross-sectional view showing an electrode layer of a lithium ion secondary battery according to an embodiment of the present invention.
  • the electrode layer 10 of this embodiment includes a positive electrode mixture layer 15 applied to one surface of a positive electrode current collector 16, a separator 13, and a negative electrode applied to the surface of a negative electrode current collector 11. And a mixture layer 12.
  • a porous insulating layer 14 is formed between the separator 13 and the positive electrode mixture layer 15 so as to cover the surface of the separator on the positive electrode mixture layer side.
  • This porous insulating layer 14 is made of a binder or polyvinylidene fluoride (PVDF) as a binder component and a melting point depressant, or a vinylidene fluoride monomer and another fluorine-containing monomer or oxygen-containing monomer. And a copolymer (hereinafter sometimes referred to as “PVDF copolymer”), and may further contain an inorganic oxide filler and / or a gas generating agent.
  • PVDF copolymer a copolymer
  • the melting temperature of the binder may be lower than the melting temperature of the separator, and for example, it is preferable to start melting in a temperature range of about 70 ° C. to about 100 ° C.
  • the porous insulating layer 14 is a pressure detection type current interrupt device (CID: Current Interrupt Device) when a predetermined battery voltage is exceeded (for example, when an overcharge state of 4.5 V or more is reached). It is preferable to promote gas generation in order to ensure that (not shown) operates.
  • CID Current Interrupt Device
  • the porous insulating layer contains an inorganic oxide filler, depending on the type and physical properties (specific surface area and particle diameter), the carbonate solvent may be decomposed during storage at high temperature or under high voltage conditions to generate gas.
  • a non-aqueous electrolyte (carbonate ester) is used. Decomposes and generates gas.
  • the gas generating compound is preferably hydrogen (H 2 ) and carbon dioxide.
  • a gas generating agent by adding a gas generating agent to the porous insulating layer 14, when a predetermined battery voltage is exceeded (for example, when an overcharged state of 4.8 V to 5.0 V is reached), The gas generating agent is decomposed to generate gas.
  • the gas generating agent is preferably a compound that generates carbon dioxide (CO 2 ).
  • a gas generating compound by adding a gas generating compound to the non-aqueous electrolyte, when a predetermined battery voltage is exceeded (for example, when an overcharged state of 4.5 V or more is reached), it decomposes and generates gas.
  • the gas generating compound is preferably hydrogen (H 2 ) and carbon dioxide.
  • the thickness of the porous insulating layer 14 is not limited as long as it can inhibit the permeation of lithium ions during melting, and is, for example, 0.1 ⁇ m to 10 ⁇ m, preferably 5 ⁇ m or less. If the thickness is less than 0.1 ⁇ m, the permeation of lithium ions may not be sufficiently inhibited during abnormal heat generation, and the heat generation suppression function cannot be exhibited reliably. When the thickness exceeds 10 ⁇ m, the resistance at normal time is increased, and the performance at the high rate as the battery characteristic is lowered.
  • the thickness of the porous insulating layer 14 may be, for example, 0.1, 0.3, 0.5, 1, 2, 5, 10 ⁇ m.
  • FIG. 2 is a cross-sectional view showing the configuration of the electrode layer 20 according to another embodiment.
  • the porous insulating layer 24 interposed between the positive electrode mixture layer 25 and the separator 23 is different from the structure shown in FIG. That is, in this embodiment, the porous insulating layer 24 is formed so as to cover the surface of the positive electrode mixture layer 25 in contact with the separator 23, but the other configuration is the same as that of the electrode layer shown in FIG. 1. .
  • the porous insulating layer may be formed between the separator and the negative electrode mixture layer (not shown), but effectively suppresses lithium ion permeation during an internal short circuit.
  • the porous insulating layer is preferably present between the positive electrode mixture layer and the separator.
  • this porous insulating layer suppresses lithium ion permeation at the time of melting, and further, when a predetermined battery voltage is exceeded, the gas generating agent is decomposed to generate gas.
  • a conductive aid or the like may be included.
  • this when providing a porous insulating layer on the surface of a positive mix layer, this may be called an overcoat layer.
  • the binder in the porous insulating layer melts below the melting temperature of the separator
  • the binder contains a melting point depressant or / and PVDF copolymer as the main component of the binder. It is considered that the melting point of PVDF is lowering.
  • the gas generating agent is decomposed to generate gas when a predetermined battery voltage is exceeded by including the gas generating agent in the porous insulating layer. It is considered based.
  • the inclusion of the inorganic filler in the porous insulating layer is based on the fact that the carbonate solvent decomposes and generates gas when a predetermined battery voltage is exceeded.
  • each component which comprises the electrode layer (10 and 20) of FIG. 1 and 2 is demonstrated in order.
  • separators 13 and 23 examples include a microporous film made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide, a porous flat plate, and a nonwoven fabric.
  • a porous resin sheet having a single-layer or multi-layer structure mainly composed of one or more polyolefin resins.
  • the thickness of the separator can be, for example, 15 ⁇ m to 30 ⁇ m.
  • a single-layer or multi-layer separator is used that has a porous resin layer that exhibits a shutdown function (when the temperature reaches a predetermined temperature, the resin melts and clogs the pores to block current). .
  • the porous insulating layers 14 and 24 are made of a binder or PVDF copolymer containing polyvinylidene fluoride (PVDF) as a binder component and a melting point depressant.
  • PVDF polyvinylidene fluoride
  • the melting start temperature and / or melting peak temperature of the binder or PVDF copolymer measured by differential scanning calorimetry in the presence of a nonaqueous electrolyte is lower than that of PVDF alone, Therefore, the porous insulating layer melts when the temperature rises and inhibits the transmission of lithium ions.
  • the porous insulating layer generates a gas to promote the operation of the pressure detection type current interrupting device when a predetermined battery voltage is exceeded (for example, when an overcharged state of 4.5 V or more). Promote.
  • Binder As a binder, polyvinylidene fluoride (PVDF) as a binder component and its melting point depressant and / or PVDF copolymer are included.
  • PVDF polyvinylidene fluoride
  • the binder component needs to be sticky to the current collector metal, which is achieved by the presence of polar groups in the binder component. Also, the binder component must be able to handle sufficient flexibility to handle the electrode and dimensional changes of the active material during the charge / discharge cycle.
  • the binder component must have specific electrochemical properties and must be compatible with the non-aqueous electrolyte solution used.
  • the mechanical and electrochemical properties of PVDF are suitable for the many purposes described above required for the binder component. Although it has been reported that the melting point of PVDF alone is about 180 ° C., it is considered that the melting point of the nonaqueous electrolyte secondary battery is slightly lowered because it is in contact with the nonaqueous electrolyte. Furthermore, by including a melting point depressant, the binder of the present embodiment melts when the temperature of the nonaqueous electrolyte secondary battery rises, increases the resistance of the conductive layer, and suppresses thermal runaway of the nonaqueous electrolyte secondary battery. be able to.
  • the melting start temperature of the binder is preferably low, but too low is not preferable because the function as the binder is hindered.
  • the melting start temperature of the binder is preferably about 50 ° C. to about 150 ° C., more preferably about 60 ° C. to about 130 ° C., and further preferably about 70 ° C. to about 110 ° C.
  • the melting peak temperature may also decrease.
  • the melting peak temperature of the binder is 70 ° C to 130 ° C.
  • the melting peak temperature of the binder is preferably 70 ° C. or higher from the viewpoint of thermal stability.
  • the melting point of the binder is preferably 130 ° C. or lower. More preferably, it is less than 130 degreeC, It is more preferable that it is 120 degrees C or less, It is still more preferable that it is 110 degrees C or less.
  • the “melting point depressant” and / or “PVDF copolymer” in the present embodiment melts the porous insulating layer at a temperature lower than that of the separator by lowering the melting start temperature and / or the melting peak temperature of the PVDF.
  • Ingredients when a porous insulating layer contains an inorganic oxide filler and a gas generating agent, it is thought that the gas generating function by them is promoted.
  • alumina used as an inorganic oxide filler may promote oxidative decomposition of carbonates contained as an electrolyte, and further promote oxidative decomposition when lithium carbonate or the like as a gas generating agent is used. It is thought that.
  • the porous insulating layer of the present embodiment has a positive electrode mixture layer and a separator. Located at the interface, an increase in battery potential can be quickly detected. Since such a function is preferably exhibited by lowering the melting start temperature and / or the melting peak temperature of the binding material, the binding material of the present embodiment has the melting start temperature of normal PVDF alone and / or Alternatively, the temperature is lower than the melting peak temperature.
  • the binder contained in the porous insulating layer of the present embodiment is a mixture of PVDF as a binder component and a melting point depressant or / and a PVDF copolymer, and the mixture is coexistent with a non-aqueous electrolyte.
  • the melting start temperature and / or the melting peak temperature when measured by the differential scanning calorimetry method can be selected as compared with the case of only PVDF measured under the same conditions.
  • the melting start temperature means the temperature at which the endotherm analyzed by differential scanning calorimetry (hereinafter also referred to as DSC) rises from the baseline, and is generally JIS7121 (plastic The transition temperature can be measured in accordance with the transition temperature measurement method.
  • the endothermic amount due to melting of the binder may be calculated from the peak area of the DSC curve, and the temperature when reaching about one-half of the total endothermic amount may be used as an index. This is because when the melting start temperature of the binder decreases, the heat absorption starts from a lower temperature and the binder melts when a certain amount of heat absorption is reached.
  • the nonaqueous electrolyte to be added to the sample is preferably an electrolytic solution in which a lithium salt containing at least LiPF 6 as an electrolyte is dissolved in a solvent mixture in which an organic solvent selected from cyclic carbonates and chain carbonates is used alone or in combination. .
  • a non-aqueous electrolyte in which 1M lithium hexafluorophosphate (LiPF 6 ) is dissolved in a 3: 7 mixed solution of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) is used.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • the temperature is raised from room temperature to about 200 ° C. at a rate of 5 ° C./min. It can obtain
  • the melting point depressant is not particularly limited as long as it is a substance that can lower the melting start temperature and the melting peak temperature of PVDF used as a binder component, but is compatible with PVDF which is a crystalline polymer (compatible) ), Preferably a crystalline or non-crystalline polymer compound.
  • the term “compatible” refers to a state in which two different substances, particularly polymers, are uniformly mixed. These are completely compatible or partially compatible. May be. It can be determined that the mixed sample is transparent or has a film-forming ability so as to be uniformly mixed. For example, it is a compound containing a carbonyl group or a cyano group.
  • the carbonyl group has a structure of —C ( ⁇ O) —, and the oxygen atom has a much higher electronegativity than the carbon atom, the electron of the C ⁇ O bond is an electron positive carbon atom. It exists in the vicinity of oxygen atoms having a higher electronegativity than in the vicinity.
  • the cyano group is a strong electron-withdrawing group having a triple structure between a carbon atom and a nitrogen atom, with electrons biased on the nitrogen atom.
  • One or a plurality of carbonyl groups and cyano groups may be contained.
  • thermodynamic parameter ⁇ 12 value representing the strength of the interaction between the two polymers, and is derived by the Flory-Huggins theory. Based on this theory, it is said that a melting point drop occurs in a compatible crystalline / amorphous polymer blend system when the ⁇ 12 value shows a negative value.
  • the compatible substance includes a carboxyl group (—COOH), a carboxylic acid ester (—COO—R), a carbonate group (R—O— (C ⁇ O) —O—R ′), an imide group ( R—CONHCO—R ′), or a crystalline or non-crystalline polymer containing an amide group (R—C ⁇ ONH—R ′).
  • the specific reason why the melting point depressant composed of such a compatible material lowers the melting point of PVDF is not clear, but the electrical properties of these additives derived from a carbonyl group or a cyano group ( It is presumed that having a polarity) enhances the interaction with PDVF and exerts its melting point lowering effect.
  • the melting point depressant is acrylic acid (AAc), methacrylic acid (MAc), acetylacetone, polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl acetate (PVAc), phthalate.
  • methacrylic acid ester having good compatibility with PVDF examples include the following compounds. Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, hexyl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, benzyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, n-butoxyethyl methacrylate, isobutoxyethyl methacrylate, t-butoxyethyl methacrylate, phenoxyethyl methacrylate, methacryl Nonylphenoxyethyl
  • methacrylic acid esters the following are preferably used from the viewpoint of easy availability and compatibility with PVDF.
  • a vinyl monomer may be used individually by 1 type, and may use 2 or more types together.
  • the fluorinated alkyl methacrylate the following compounds can be preferably used. 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4 -Hexafluorobutyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2,2-trifluoroethyl ⁇ -fluoroacrylate, 2,2,3,3-tetra Fluoropropyl ⁇ -fluoroacrylate, 2,2,3,3,3-pentafluoropropyl ⁇ -fluoroacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl ⁇ -fluoroacrylate, and the like.
  • the melting point depressant includes amide, imide, maleimide and the like.
  • a primary amide is particularly preferable, and examples thereof include N-vinylamide, divinylamide, silyl (vinyl) amide, glyoxylated vinylamide and the like.
  • the imide include divinylimide such as N-vinylimide, N-vinylphthalimide, and vinylacetamide.
  • maleimides include monomaleimide, bismaleimide, trismaleimide, and polymaleimide.
  • bismaleimide examples include, for example, N, N′-bismaleimide-4,4′-diphenylmethane, 1,1 ′-(methylenedi-4,1-phenylene) bismaleimide, N, N ′-(1, 1′-biphenyl-4,4′-diyl) bismaleimide, N, N ′-(4-methyl-1,3-phenylene) bismaleimide, 1,1 ′-(3,3′-dimethyl-1,1 '-Biphenyl-4,4'-diyl) bismaleimide, N, N'-ethylenedimaleimide, N, N'-(1,2-phenylene) dimaleimide, N, N '-(1,3-phenylene) dimaleimide N, N'-thiodimaleimide, N, N'-dithiodimaleimide, N, N'-ketone dimaleimide, N, N'-methylenebismaleimide, bismaleimide methyl methyl
  • the melting point depressant includes amide, imide, maleimide and the like.
  • the content of these melting point depressants and / or PVDF copolymers contained in the binder is preferably 1 to 50% by mass, more preferably 2 to 40% by mass, and still more preferably. Is 5-30% by mass. If the content of the melting point depressant is less than 1% by mass, the melting point depressing action of the binder component is small.
  • the binder of this embodiment is obtained by dissolving polyvinylidene fluoride (PVDF) as a binder component and a melting point depressant or / and PVDF copolymer in a common solvent that dissolves them together, followed by solvent replacement. It is preferred to prepare as a precipitated mixture. This is because the binder prepared by this method exists in a state where the binder component and the melting point depressant are uniformly mixed at the molecular level.
  • PVDF polyvinylidene fluoride
  • a powder mixture of polyvinylidene fluoride (PVDF) and a melting point depressant or / and a PVDF copolymer is mixed with a powder mixer such as a ball mill or a rocking mixer or a known crusher. May be prepared. This is because it is easily uniformized in a solvent for preparing the electrolytic solution or electrode mixture layer to become a binder.
  • PVDF polyvinylidene fluoride
  • the melting point depressant may be a copolymer (PVDF copolymer) of a vinylidene fluoride monomer and another fluorine-containing monomer or oxygen-containing monomer.
  • fluorine-containing monomers include vinyl fluoride, 3-fluorinated propylene, and fluoroalkyl vinyl ether
  • oxygen-containing monomers include ethylene glycol.
  • PVDF-HFP poly (vinylidene fluoride-hexafluoropropylene)
  • PVDF-PEO poly (vinylidene fluoride-oxyethylene)
  • PVDF polyvinylidene fluoride
  • a polyvinylidene fluoride (PVDF) copolymer containing PVDF as a binding component and a melting point depressant in the molecule may be used as the binder.
  • PVDF polyvinylidene fluoride
  • the melting start temperature and / or the melting peak temperature of the PVDF copolymer is lower than that of PVDF, which is a vinylidene fluoride single polymer.
  • PVDF which is a vinylidene fluoride single polymer.
  • it has a melting start temperature and / or a melting peak temperature at 45 ° C. to 110 ° C., more preferably 50 ° C. to 100 ° C.
  • PVDF-HFP hexafluoropropylene
  • PVDF-PEO polyoxyethylene
  • the melting start temperature and / or the melting peak temperature can be adjusted to a desired temperature and used.
  • the porous insulating layer preferably further contains an inorganic oxide filler.
  • an inorganic oxide filler aluminum oxide ( ⁇ -Al 2 O 3 , ⁇ -Al 2 O 3 ), aluminum hydroxide (Al (OH) 3 ), boehmite (AlOOH)), magnesia (magnesium oxide: MgO) , Magnesium hydroxide (Mg (OH) 2 ), zirconia (ZrO 2 ), titania (TiO 2 ), silica (SiO 2 ), silicon dioxide (SiO 2 ), silicon carbide (SiC), aluminum nitride (AlN) or nitride Boron (BN) or the like is used.
  • the shape of the inorganic oxide filler is not limited, and various shapes such as a spherical shape, a needle shape, an ellipsoid shape, a plate shape, and a scale shape can be used.
  • the average particle size is not particularly limited, but is preferably 0.01 to 5 ⁇ m.
  • the “average particle diameter” means a cumulative 50 volume% from the fine particle side in the volume-based particle size distribution measured by a particle size distribution measuring apparatus based on a general laser diffraction / light scattering method. corresponding particle size (D 50 particle size, median diameter) to refer to.
  • the content of the inorganic oxide filler in the porous insulating layer is 0 to 99% by mass, preferably about 80 to 90% by mass. Increasing the added amount of the inorganic oxide filler contributes to the heat resistance of the separator, and if the added amount of the inorganic oxide filler is reduced as much as possible, it becomes a porous insulating layer that adheres to the separator and becomes a binder during internal short circuit. Melts and contributes to improved safety. Furthermore, by selecting the type and physical properties of the inorganic oxide filler, it is possible to decompose the electrolyte and generate gas when the battery is overcharged.
  • the gas generating agent in the present embodiment is a compound that can decompose and generate gas when a predetermined battery voltage is exceeded (for example, when an overcharged state of 4.8 to 5.0 V is reached). Not limited. Preferably, it is a compound that decomposes to generate carbon dioxide gas, and is lithium carbonate (Li 2 CO 3 ), lithium hydrogen carbonate (LiHCO 3 ), sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, sodium bicarbonate, carbonate One or more selected from potassium hydrogen, magnesium hydrogen carbonate, calcium hydrogen carbonate, 4,4′-oxybis (benzenesulfonylhydrazide) (OBSH), azodicarbonamide (ADCA) and the like can be used.
  • OBSH 4,4′-oxybis (benzenesulfonylhydrazide)
  • ADCA azodicarbonamide
  • the content of the gas generating agent in the porous insulating layer is 0 to 10% by mass, preferably about 0.5 to 5% by mass. Further, when the porous insulating layer contains both the inorganic oxide filler and the gas generating agent, the content ratio of the gas generating agent to the inorganic oxide filler is preferably 90:10 to 99: 1.
  • the above binder and, if desired, an inorganic oxide filler and a gas generating agent are represented by water, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, dimethylformamide, ⁇ -butyrolactone, or the like.
  • the aprotic polar solvent or a slurry obtained by dissolving or dispersing in the mixed solution can be applied to the electrode mixture layer or the surface of the separator and dried. By drying after slurry application, the dispersion solvent (water or organic solvent) volatilizes and opens to form a porous layer. The size of the pores at this time can be increased by adding a small amount of an inorganic oxide filler.
  • CHB and BP mixed in the porous layer are eluted when they come into contact with the carbonate-based electrolytic solution, they exhibit the same effect as when these gas generating agents are added to the electrolytic solution.
  • the size and amount of the pores can be adjusted by the slurry solid content concentration and the drying speed.
  • a slurry in which an inorganic oxide filler, a gas generating agent, and a binder are mixed in a ratio of 76: 4: 20 to 94: 5: 1 is applied to the surface of the positive electrode mixture layer and dried to obtain a positive electrode composite. It can be produced by forming a porous insulating layer on the surface of the agent layer and compressing it to a predetermined thickness by a roll press.
  • the positive electrode active material is not particularly limited as long as it is a material capable of occluding and releasing lithium, and may be a positive electrode active material usually used in lithium ion secondary batteries.
  • a positive electrode active material usually used in lithium ion secondary batteries.
  • at least one metal element other than lithium and nickel that is, a transition metal element other than Li and Ni and (Or a typical metal element) is also meant to include an oxide containing a constituent metal element in a proportion equivalent to or less than nickel in terms of the number of atoms.
  • metal element other than Li and Ni examples include, for example, Co, Mn, Al, Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, It may be one or more metal elements selected from the group consisting of La and Ce. These positive electrode active materials may be used alone or in combination.
  • the positive electrode active material includes, for example, the general formula (1): Li t Ni 1-xy Co x Al y O 2 (wherein 0.95 ⁇ t ⁇ 1.15, 0 ⁇ x ⁇ 0.3, 0.1 ⁇ y ⁇ 0.2, and x + y ⁇ 0.5 are satisfied.) Lithium nickel cobalt aluminum-based oxide (NCA).
  • NCA Lithium nickel cobalt aluminum-based oxide
  • a specific example of NCA is LiNi 0.8 Co 0.15 Al 0.05 O 2 .
  • a lithium nickel cobalt manganese-based oxide (NCM) is given.
  • NCM has a high energy density per volume and excellent thermal stability.
  • the content of the positive electrode active material in the electrode mixture layer is usually 10% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more, and particularly preferably 70% by mass or more. Moreover, it is 99.9 mass% or less normally, Preferably it is 99 mass% or less.
  • Negative electrode active materials include metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped / undoped with lithium ions, and transition metals that can be doped / undoped with lithium ions At least one selected from the group consisting of nitrides and carbon materials capable of doping and undoping lithium ions (may be used alone or a mixture containing two or more of these may be used) Can be used.
  • Examples of metals or alloys that can be alloyed with lithium (or lithium ions) include silicon, silicon alloys, tin, and tin alloys. Further, lithium titanate may be used. Among these, carbon materials that can be doped / undoped with lithium ions are preferable. Examples of such carbon materials include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), amorphous carbon materials, and the like. The form of the carbon material may be any of a fibrous form, a spherical form, a potato form, and a flake form.
  • amorphous carbon material examples include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500 ° C. or less, and mesophase pitch carbon fiber (MCF).
  • MCMB mesocarbon microbeads
  • MCF mesophase pitch carbon fiber
  • Examples of the graphite material include natural graphite and artificial graphite.
  • artificial graphite graphitized MCMB, graphitized MCF, and the like are used.
  • a material containing boron can be used.
  • the graphite material those coated with a metal such as gold, platinum, silver, copper and tin, those coated with amorphous carbon, and those obtained by mixing amorphous carbon and graphite can be used. These carbon materials may be used alone or in combination of two or more.
  • an electrode mixture layer contains a conductive support agent.
  • a known conductive auxiliary agent can be used as the conductive auxiliary agent used in the present invention.
  • the known conductive aid is not particularly limited as long as it is a carbon material having conductivity, but graphite, carbon black, conductive carbon fiber (carbon nanotube, carbon nanofiber, carbon fiber), fullerene, etc. It can be used alone or in combination of two or more.
  • Examples of commercially available carbon black include Toka Black # 4300, # 4400, # 4500, # 5500 (Tokai Carbon Co., Furnace Black), Printex L and the like (Degussa Co., Furnace Black), Raven 7000, 5750, 5250, 5000 ULTRA III, 5000 ULTRA, etc., Conductex SC ULTRA, Conductex 975 ULTRA, etc., PUER BLACK100, 115, 205, etc. (manufactured by Colombian, Furnace Black), # 2350, # 2400B, # 2600B, # 30050B, # 3030B, # 3030B, # 3030B 3350B, # 3400B, # 5400B, etc.
  • the content of the conductive additive contained in the electrode mixture layer is preferably 1% by mass or more, and is preferably about 1 to 10% by mass, for example, natural graphite such as artificial graphite, flake graphite, lump graphite, and earth graphite However, it is not limited to these.
  • the content of the conductive additive contained in the electrode mixture layer is preferably 1% by mass or more, and is preferably about 1 to 10% by mass, for example, natural graphite such as artificial graphite, flake graphite, lump graphite, and earth graphite However, it is not limited to these.
  • the content of the conductive additive contained in the electrode mixture layer is preferably 1% by mass or more, and is preferably about 1 to 10% by mass, for example, natural graphite such as artificial graphite, flake graphite, lump graphite, and earth graphite However, it is not limited to these.
  • the content of the conductive additive contained in the electrode mixture layer is preferably 1% by mass or more, and is preferably about 1
  • Examples of the positive electrode current collector (16 or 26) include aluminum, nickel, and SUS, and examples of the negative electrode current collector (11 or 21) include copper, nickel, and SUS. .
  • aluminum and copper are preferable from the balance between high conductivity and cost.
  • Aluminum means aluminum and aluminum alloy
  • copper means pure copper and copper alloy.
  • the aluminum foil can be used on the secondary battery positive electrode side, the secondary battery negative electrode side, and the copper foil on the secondary battery negative electrode side.
  • A1085 material which is a pure aluminum type, and A3003 material, can be used.
  • it is the same also as copper foil Although it does not specifically limit, Rolled copper foil and electrolytic copper foil are used preferably.
  • the electrode layer included in the lithium ion secondary battery of the present embodiment is obtained by applying the electrode mixture slurry containing the electrode active material, the conductive auxiliary agent, and the binder described above to the surface of the current collector and drying it.
  • the binder for binding the electrode active material a fluorine resin typified by PVDF, a polysaccharide polymer, SBR, or the like can be used, but is not limited thereto.
  • the binder contained in the said porous insulating layer can also be used. In this case, it is preferable to form an electrode mixture slurry by dispersing the electrode active material and the conductive additive in a solution obtained by dissolving the binder described above in a solvent.
  • the solvent contained in the mixture slurry also serves as a common solvent for preparing the above binder, and is a non-proton represented by N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, dimethylformamide, ⁇ -butyrolactone, etc. Polar solvent or a mixture thereof can be selected.
  • the application and drying method is not particularly limited.
  • methods such as slot die coating, slide coating, curtain coating, or gravure coating may be used.
  • the drying method include drying with warm air, hot air, low-humidity air, vacuum drying, and (far) infrared rays.
  • the drying time and drying temperature are not particularly limited, but the drying time is usually 1 minute to 30 minutes, and the drying temperature is usually 40 ° C. to 180 ° C.
  • the method for producing a mixture layer has a step of reducing the porosity of the active material layer by pressure treatment using a die press or a roll press after applying and drying the above mixture slurry on a current collector. Is preferred.
  • the electrolyte solution is preferably one that is usually used in a lithium ion secondary battery, and specifically has a form in which a supporting salt (lithium salt) is dissolved in an organic solvent.
  • a supporting salt lithium salt
  • the lithium salt include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), six Inorganic acid anion salts such as lithium fluorotantalate (LiTaF 6 ), lithium tetrachloroaluminate (LiAlCl 4 ), lithium decachlorodecaborate (Li 2 B 10 Cl 10 ), lithium trifluoromethanesulfonate (LiCF 3) Organic acids such as SO 3 ), lithium bis (trifluoromethanesulfonyl) imide (Li (CF 3 SO 2 )
  • organic solvent examples include cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, fluorine-containing chain carbonates, aliphatic carboxylic acid esters, fluorine-containing aliphatic carboxylic acid esters, and ⁇ -lactone.
  • Fluorine-containing ⁇ -lactones, cyclic ethers, fluorine-containing cyclic ethers, chain ethers, and at least one organic solvent selected from the group consisting of fluorine-containing chain ethers can be used.
  • cyclic carbonates examples include propylene carbonate (PC), ethylene carbonate (EC), and butylene carbonate (BC).
  • fluorine-containing cyclic carbonate fluoroethylene carbonate (FEC) can be mentioned, for example.
  • chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and dipropyl carbonate (DPC).
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • MPC methyl propyl carbonate
  • EPC ethyl propyl carbonate
  • DPC dipropyl carbonate
  • aliphatic carboxylic acid esters examples include methyl formate, methyl acetate, and ethyl propionate.
  • examples of ⁇ -lactones include ⁇ -butyrolactone.
  • examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, and 1,4-dioxane.
  • examples of the chain ethers include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, and 1,2-dibutoxyethane.
  • Other examples include nitriles such as acetonitrile and amides such as dimethylformamide. These can be used alone or in combination of two or more.
  • the electrolyte may further contain a gas generating compound.
  • This gas generating compound may be added directly to the electrolytic solution, or may be eluted from the porous insulating layer into the electrolytic solution inside the battery.
  • the gas generating compound contained in the electrolytic solution is a compound that can decompose and generate gas when a predetermined battery voltage is exceeded (for example, when an overcharged state of 4.5 V or more is reached).
  • the gas generating compound is preferably a compound that generates hydrogen, and is selected from the group consisting of cycloalkylbenzene compounds (for example, cyclohexylbenzene (CHB)), alkylbenzene compounds, biphenyl compounds (for example, biphenyl (BP)), and alkylbiphenyl compounds. One or more of these can be added.
  • the amount of the gas generating compound added to the electrolytic solution is not particularly limited as long as a predetermined amount of gas is generated under a predetermined condition. For example, it is about 0.05 to 5.0% by mass, preferably 0.1 to It is 4.0 mass%.
  • the binder in the porous insulating layer formed between the electrode and the separator melts and the lithium ion secondary there is an effect of inhibiting the permeation, thereby suppressing the heat generation at the time of internal short circuit of the battery.
  • a gas such as hydrogen (H 2 ) or carbon dioxide (CO 2 ) is generated from the porous insulating layer formed between the electrode and the separator against a gradual temperature increase during overcharge. This is advantageous in that it promotes the operation of a pressure-sensitive current interrupting device (CID: CURRENT Interrupt Device).
  • Example preparation> PVDF and various melting point depressants (powder) were mixed at a predetermined ratio for about 15 minutes using an agate mortar.
  • a mixing ratio of PVDF (powder) and melting point depressant (powder) was 1: 1
  • 0.1 g was weighed and mixed.
  • This mixed powder was vacuum dried at room temperature (25 ° C.) for 10 hours or more.
  • 3 mg of the above sample was weighed into a SUS-PAN for DSC measurement that had been weighed in advance.
  • the lid (weighed in advance) was quickly set (weighed) and hermetically sealed with a dedicated press.
  • Table 2 shows the PVDF manufacturer name and product name, and the melting temperature of PVDF alone.
  • Table 3 shows the melting start temperature and peak temperature (melting point) when 75% by mass of the binder component (PVDF) and 25% by mass of the melting point depressant or 50% by mass of each were mixed.
  • FIG. 3 shows a PVDFW # 7200 powder sample (solid line) shown in Table 2 or a sample in which an electrolyte coexists with this (dotted line), and a sample obtained by adding 25% PMMA to PVDFW # 7200 (Table 3).
  • the first line from the top) shows a DSC chart. From the results shown in FIG. 3, it can be seen that the melting start temperature and melting point of PVDF, which is a binder component, are clearly reduced by the addition of a melting point depressant.
  • Seikyokusaku made 1. Preparation of positive electrode mixture layer slurry A 5 L planetary dispa was used for slurry preparation. 920 g of NCM523 (commercial formula LiNi 0.5 Co 0.2 Mn 0.3 O 2 , manufactured by Umicore), 20 g Super-P (conductive carbon manufactured by TIMCAL), KS-6 (flaky graphite manufactured by TIMREX) After mixing 20 g for 10 minutes, 100 g of N-methylpyrrolidone (NMP) was added and further mixed for 20 minutes.
  • NMP N-methylpyrrolidone
  • Coating / Drying A die coater was used for slurry coating. The slurry was applied to one side of an aluminum foil (thickness 20 ⁇ m, width 200 mm) so that the coating weight after drying was 19.0 mg / cm 2 and dried. Next, the slurry was applied to an aluminum foil on the opposite surface (uncoated surface) in the same manner so that the coating weight was 19.0 mg / cm 2 and dried. A positive electrode with a double-sided coating (38.0 mg / cm 2 ) thus obtained was prepared (CA-1).
  • Overcoat layer slurry preparation A 5 L planetary dispa was used for slurry preparation. 860 g of lithium carbonate, 100 g of Super-P (conductive carbon manufactured by TIMCAL), 250 g of 8% -PVDF solution (PVDFW # 7200 manufactured by Kureha dissolved in NMP), 20 g of polymethyl methacrylate (PMMA), N-methylpyrrolidone (PMMA) NMP) 540 g was added and mixed for 30 minutes. Next, 1125 g of NMP was added and the mixture was further mixed for 60 minutes, and then vacuum defoaming was performed for 30 minutes to prepare a slurry having a solid content concentration of 32%.
  • Coating / Drying As with the positive electrode mixture layer, a die coater was used for slurry coating. The slurry was applied to one side of an aluminum foil (thickness 20 ⁇ m, width 200 mm) coated with the positive electrode mixture layer so that the coating weight after drying was 2.0 mg / cm 2 and dried. Furthermore, it was applied to the other side and dried. In this way, a positive electrode CB-1 coated with an overcoat layer (OC-1) was obtained.
  • the electrode was slit to obtain a positive electrode C-1 so that an electrode application area (surface: 56 mm ⁇ 334 mm, back: 56 mm ⁇ 408 mm) and a tab welding margin were obtained.
  • Coating / Drying A die coater was used for slurry coating. The slurry was applied to one side of a copper foil (thickness 10 ⁇ m) and dried so that the coating weight after drying was 11.0 mg / cm 2 . Next, the slurry was applied to a copper foil on the opposite surface (uncoated surface) in the same manner so that the coating weight was 11.0 mg / cm 2 and dried. The double-sided coated (22.0 mg / cm 2 ) negative electrode roll thus obtained was dried at 120 ° C. for 12 hours in a vacuum drying oven.
  • the electrode was slit to obtain an electrode application area (front surface: 58 mm ⁇ 372 mm, back surface: 58 mm ⁇ 431 mm) and a tab welding margin, and negative electrode A-1 was obtained.
  • Example 2 A positive electrode and a negative electrode were produced in the same manner as in Example 1 except for the preparation of the overcoat layer slurry.
  • Overcoat layer slurry was prepared by adding 250 g of an 8% -PVDF-HFP solution (ARKEMA FLEX2751 dissolved in NMP) instead of PMMA used in Example 1 to prepare an overcoat layer slurry (OC-2). Coating and drying were performed in the same manner as in Example 1 to obtain positive electrode CB-2 coated with an overcoat layer (OC-2).
  • Example 3 A positive electrode and a negative electrode were produced according to Example 1 except for the preparation of the overcoat layer slurry.
  • the overcoat layer slurry was prepared using a 5 L planetary dispa. 430 g of ⁇ -alumina (Al 2 O 3 ) having a particle size of 2 ⁇ m and a specific surface area of 2 m 2 / g, 430 g of lithium carbonate, 100 g of Super-P (conductive carbon manufactured by TIMCAL), 8% -PVDF solution (PVDFW # 7200 manufactured by Kureha) Was dissolved in NMP), 250 g of 8% -PVDF-HFP solution (ARKEMA FLEX2751 dissolved in NMP) was added to 540 g of N-methylpyrrolidone (NMP) and mixed for 30 minutes. Next, 1125 g of N-methylpyrrolidone (NMP) was added and mixed for another 60 minutes, followed by vacuum defoaming for 30 minutes to prepare a slurry (OC-
  • Example 3 In the same manner as in Example 1, a die coater was used for slurry coating. The slurry was applied to one side of an aluminum foil (thickness 20 ⁇ m, width 200 mm) coated with the positive electrode mixture layer so that the coating weight after drying was 2.0 mg / cm 2 and dried. Furthermore, it was applied to the other side and dried. In this way, a positive electrode CB-3 coated with an overcoat layer (OC-3) was obtained.
  • Example preparation Aluminum tabs in the margin of the positive electrode for testing (single-sided coating, electrode surface 30 mm x 30 mm) with various specifications for the overcoat layer shown in Table 5 on the positive electrode (C-1) consisting of the positive electrode specifications shown in Table 4 Were joined by an ultrasonic joining machine (CK1). A nickel tab was joined to an 2.8 cm ⁇ 2.8 cm negative electrode Cu foil having the negative electrode specification (A-1) shown in Table 4 with an ultrasonic bonding machine (AK1). AK1 was brought into contact with the coated surface of CK1 with a PE separator in between, and sandwiched between 5 cm ⁇ 5 cm laminate sheets, and the three sides were heat-sealed.
  • CK1 ultrasonic joining machine
  • the prepared sample cell (K1) is sandwiched between heat blocks at a restraining pressure of 0.2 kgf / cm 2 , and the measurement conditions are, for example, that the temperature is raised from room temperature to about 200 ° C. at 5 ° C./min. At this time, an AC resistance value ( ⁇ ) at each frequency (eg, 1 kHz, 10 kHz, 100 kHz) can be obtained. An example of the result is shown below. Table 6 shows the resistance increase start temperature and the maximum resistance value measured for the sample.
  • Reference Example 1 is a test result obtained using a positive electrode without an overcoat layer.
  • a 5 L planetary dispa was used for slurry preparation.
  • ⁇ -Alumina (Al 2 O 3 ), PVDF (Solef 5130 from Solvay), lithium carbonate, cyclohexylbenzene (CHB) and biphenyl (BP) having a particle size of 2 ⁇ m and a specific surface area of 2 m 2 / g are shown in Table 7 below.
  • a slurry for porous insulating layer was prepared by dispersing in water or N-methylpyrrolidone (NMP) at a ratio.
  • NMP N-methylpyrrolidone
  • a separator base material (50% porosity and 16 ⁇ m thickness) was prepared by laminating a PP layer, a PE layer, and a PP layer in order.
  • the slurry for porous insulation layers was apply
  • a separator having a porous insulating layer (having a thickness of 4 to 5 ⁇ m) on one surface of the porous substrate was obtained.
  • the prepared sample cell (K1) is sandwiched between heat blocks at a restraining pressure of 0.2 kgf / cm 2 , and the measurement conditions are, for example, that the temperature is raised from room temperature to about 200 ° C. at 5 ° C./min. At this time, an AC resistance value ( ⁇ ) at each frequency (eg, 1 kHz, 10 kHz, 100 kHz) can be obtained. An example of the result is shown below. Table 8 shows the resistance increase start temperature and the maximum resistance value measured for the sample. Reference Example 2 shows the results of a test conducted using a separator without a porous insulating layer.
  • Winding type battery (design capacity 1Ah) 1. Winding Using the overcoat layer shown in Table 5 or the separator with a porous heat-resistant layer shown in Table 7 (60.5 mm ⁇ 450 mm), a wound battery (design capacity 1 Ah) was produced. Negative electrode A-1 (front surface / back surface), separator (positioned so that the porous insulating layer is in contact with positive electrode C-1), positive electrode C-1 (back surface / front surface), separator (the porous insulating layer is positive electrode C-1) The sheet was placed in contact with each other, wound up, and press-molded.
  • an aluminum tab was joined to the blank portion of the positive electrode C-1 with an ultrasonic bonding machine, and a nickel tab was joined to the blank portion of the negative electrode A-1 with an ultrasonic bonding machine. This was sandwiched between laminate sheets and heat-sealed on the three sides.
  • overcoat layer batteries manufactured with the same specifications as in Example 1 (batteries having positive electrodes with overcoat specifications OC-2 to OC-11 shown in Table 5 are shown in Examples 2 to 11. )
  • separator-type batteries (batteries having separators with OC-101 and OC102 insulating layer specifications in Table 7 are referred to as Reference Examples 101 and 102).
  • a wound battery (design capacity 1 Ah) was manufactured using a separator having no overcoat layer in the same specifications as in Reference Example 101 (Comparative Example 2). When the same crushing test was performed 5 times, the heat generation suppressing effect could not be confirmed in all cases.

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Abstract

Dans la présente invention, une couche d'isolation poreuse est formée entre une électrode et un séparateur de sorte que, lorsque la température de la batterie augmente, la couche d'isolation poreuse fond et bloque la transmission des ions lithium, supprimant ainsi la production de chaleur lorsqu'un court-circuit interne se produit dans la batterie. L'accumulateur au lithium-ion de la présente invention comprend des électrodes, chacune comportant un collecteur et une électrode positive ou une électrode négative sur au moins une des surfaces du collecteur, un séparateur séparant l'électrode positive et l'électrode négative l'une de l'autre, la couche d'isolation poreuse formée entre l'électrode et le séparateur, et un électrolyte non aqueux. La couche d'isolation poreuse comprend un matériau de liaison contenant du polyfluorovinylidène (PVDF) et un agent d'abaissement du point de fusion. L'agent d'abaissement du point de fusion abaisse la température de début de fusion et/ou la température maximale de fusion du matériau de liaison par rapport au PVDF seul, tel que mesuré par calorimétrie différentielle à balayage en présence de l'électrolyte non aqueux.
PCT/JP2018/012290 2017-03-30 2018-03-27 Accumulateur au lithium-ion WO2018181243A1 (fr)

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